Dielectric and electrical properties of PEO-Al2O3 nanocomposites

Complex dielectric permittivity, electric modulus, alternating current electrical conductivity and impedance spectra of polymer nanocomposites (PNCs) consisting of poly(ethylene oxide) (PEO) matrix dispersed with alumina (Al2O3) nanoparticles (i.e., PEO-x wt% Al2O3, where x is 0, 1, 3 and 5) have been investigated in the frequency range from 20 Hz to 1 MHz at 30 degrees C. It is found that the complex permittivity values abruptly decrease on dispersion of 1 wt% content of nanosize Al2O3 particles in the PEO matrix which vary slightly with further increase of nanofiller concentration up to 5 wt%. At radio frequencies, the real part of permittivity and dielectric loss values are found nearly 2 and 0.03, respectively, confirming the suitability of these PNCs as low-permittivity polymeric nanodielectrics. The increased values of dielectric and electric modulus relaxation times of the PNCs confirm that the electrostatic interactions between Al2O3 nanoparticles and polar groups of PEO produce hindrance to the polymer chain segmental dynamics. The temperature dependent investigation on PEO-3 wt% Al2O3 film reveals that the dielectric properties, electrical conductivity and the molecular chain segmental dynamics increase with the increase of temperature confirming the thermally activated dielectric behaviour of the PNC film. The variation of dc conductivity and dielectric relaxation time with the change in temperature from 30 degrees C to 60 degrees C of the PNC film obeys the Arrhenius behaviour. The XRD study infers that the crystalline phase of PEO matrix decreases with the increase of Al2O3 concentration in the nanocomposites. The variation in values of dielectric permittivity, polymer chain segmental dynamics, amorphous phase, and the conductivity and relaxation times activation energies have been considered to explore the feasibility of these PNC materials for the technological applications. (C) 2017 Elsevier B.V. All rights reserved.